#include<bits/stdc++.h>
using namespace std;

#define pb push_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
const int maxn = 3e5 + 70;
const int INF = 0x3f3f3f3f;
const ll inf = 0x3f3f3f3f3f3f3f3f;
const int MOD = 1e9 + 7;
const double eps = 1e-7;
const double PI = acos(-1.0);

int calc(int x){
    for(int i=2;i*i<=x;i++){
        if(x % i == 0) return i;
    }
    return x;
}

int main(){
    //freopen("in.txt", "r", stdin);
    int T; cin >> T;
    while(T--){
        int a, b; scanf("%d %d",&a,&b);
        if(a > b) swap(a, b);

        if(b == 1) printf("-1 -1\n");
        else{
            int x = b - a;
            if(x == 0) printf("%d %d\n",2,a);
            else if(x == 1) printf("-1 -1\n");
            else printf("%d %d\n",calc(x), x);
        }
    }
    return 0;
}